Esters of thiophene-modified maleic anhydride-styrene copolymers and oil compositions containing the same



Patented June 17, 1952 UNITED STATES PATENT OFFICE ESTERS OF THIOPHENE-MODIFIED MALEIC AN HYDRIDE STYRENE COP OLYMERS AND OIL COMPOSITIONS CONTAINING THE SAME Ferdinand P. Otto and Orland M. Reiff, Woodbury, N. J., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing.

Application September 29, 1949, Serial No. 118,708

11 Claims. (Cl. 252-486) and Robert W. Barrett, lubricating oil compositions containing copolymers of styrene and maleic anhydride, esterified with aliphatic alcohols having from about 10 to about 18 carbon atoms as V. I. improvers and pour point de- 1 pressants are disclosed and claimed.

As is well known, mineral lubricating oils tend to decompose, especially under heat and oxidizing conditions, such as those encountered in use in internal combustion engines. The decom-,

position products formed in the oil are acidic 20 in nature and exert a corrosive action upon the metal surfaces being lubricated.

We have now found that when styrene is copolymerized with maleic anhydride in the presence of thiophene, or alkyl thiophenes, thiophene-type sulfur is introduced into the copolymer molecule. We have found further that the sulfur-containing polymer products may then be esterified with primary, normal, saturated alcohols having from about 10 to about 18 carbon atoms, to provide products, which are not only efiective viscosity index improvers and pour point depressants for lubricating oils, but which are also efiective antioxidants for lubricating oils.

Thus, these ester products inhibit the tendency of such oils to decompose in use and thereby retard the normal corrosive effects exerted by the oil on the metal surfaces being lubricated.

It is the primary object of this invention to provide improved lubricating oil compositions containing the thiophene-modified, styrenemaleic anhydride esters herein contemplated. Other objects will become apparent from what follows.

As far as is known, the esterified thiophenamodified styrene-maleic anhydride copolymers have not been known heretofore, and they are, therefore, contemplated herein as new compositions of matter.

The thiophene compounds suitable for u se in preparing the polymer products of the invention may be represented by the general formula s where R, R R and R represent hydrogen or alkyl groups, which may be. straight, branchchained or cycloaliphatic in structure. As typical examples of suitable thiophene compounds, there may be mentioned thiophene per se, 2- nethyl thiophene, B-meth'yl thiophene, 2-tertiarybutyl thiophene, 2,5-di-tertiary-butyl thiophene, 2,3,5-trimethyl thiophene, 2,3,4,5-tetra-methyl thiophene, 2,5-dimethyl, 3,4-diethyl thiophene, 2-cyclohexyl thiophene, 2-dodecy1 thiophene, 2- octadecyl thiophene, 2-wax thiophene and 2,-5- di-wax thiophene.

The esterified thiophene-modified copolymer 6 products of the invention are prepared by, first,

reacting together maleic anhydride and styrene in the presence of the thiophene derivative to form the thiophene-modified, maleic anhydridestyrene copolymer and then esterifying the product with the alcohol.

Substantially equimolar quantities of maleic anhydride and styrene are employed in the copolymerization reaction, the thiophene compound being present in at least about equimolar amount; and preferably in excess, the preferred amount being from about 4 to about 10 moles per mole of maleic anhydride or styrene, since these latter amounts provide products having the largest percentages of thiophene incorporated therein.

The reaction may also be carried out with the aid of benzene, xylene, dioxane or the like as solvent materials where desirable.

Suitable reaction temperatures range from about C. to about C., the normal practice being to utilize a temperature sufiicient to maintain the reaction mixture at gentle reflux. The time of reaction varies between about 1 and about 10 hours, however, the reaction is generally completed in from about 2 to about '7 hours.

We have found that a catalyst is unnecessary,

although the reaction is facilitated by the use of a small amount, from about 1 to 5 Weight percent, based on the amountof maleic anhydride used, of an organic peroxide catalyst, such as benzoyl peroxide.

The thiophene-modified copolymer product is esterified with a primary, normal, saturated, aliphatic alcohol to produce the esterified copolymers of the invention. The esterification reaction is effected under ordinary esterification conditions,-i. e. by heating the copolymer and the alcohol in the presence of strong sulfuric acid.

The saturated, normal alcohols suitable for providing the products herein contemplated are those having from about 10' to about 18 carbon atoms. Any of these alcohols will yield ester products which are effective as V. I. improvers in mineral oils. However, only those relatively pure alcohols having from 14 to 16 carbon atoms, or a mixture of alcohols having an average of about 14 carbon atoms, will provide products which are efiective as pour point depressants.

Specifically, the alcohols which we may use are decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and .octadecyl alcohols. A preferred alcohol reactant, however, is Lorol-B. This is a mixture of alcohols marketed by E. I. du Pont de Nemours 8a Company, which contains saturated, straight-chain alcohols in the following approximate proportions: 2.5% of C10 alcohols, 55.0% of C-12 alcohols, 20.5% of C-14 alcohols, 9.0% of C-16 alcohols and 13.0% of C-18 alcohols; the average chain length of the alcohols being 13.5 carbon atoms per molecule A more complete understanding of the invention will be had from the following examples illustrating detailed procedures which may be conveniently followed in preparing our new rear tion products.

EXAMPLE I THIOPHENE-MODIFIED STYBENE-MALEIc ANHYDRIDE GoroLYMER Reaction mixture Grams Maleic anhydride 24.5

Styrene 25.5 'Ihiophene 200.0 Benzoyl peroxide 1.0

These reactants were placed in a liter stainless steel stirring-type autoclave. The autoclave temperature was maintained at 121 C. for a period of 6 hours. The product, a brittle, thiophene-insoluble material, was then isolated by filtration and dissolved in acetone. By pouring this solution into methanol, filtering and drying the precipitate, there was obtained 37 grams of a pale brown, amorphous powder containing 2.1% sulfur.

EXAMPLE II 2-1\'IETHYLTHIOPHENE-1\IODIFIED STYRENE-M'ALEIC ANHYDBIDE GOPOLYMEB Reaction mixture Maleic anhydride A grams 49 Styrene do 40 2-methylthiophene cc 500 Benzoyl peroxide gram 1.0

These reactants were placed in a 3-neck, round-bottom flask equipped with a reflux condenser, thermometer and mechanically driven stirrer. The mixture was then refluxed for a period of hours at 1'16" C. The product, an amorphous, pale brown, insoluble material, was isolated from the solvent layer by decantation, and then dissolved in acetone. By pouring this solution into methanol, filtering and drying the precipitate, there was obtained 53 grams of a pale brown, amorphous powder containing 3.3% sulfur. A saponification value of 537 indicated that the product contains 47% by weight of maleic anhydride.

EXAMPLE III li-METHrLrfildrHENE-MODIFIED STYRENu-MALEiC ANHYDBIDE COIOLYMER Reaction mixture Maleic anhydride grams 49 Styrene do 50 3-methylthiophene cc 500 Benzoyl peroxide gram 1.0

These reactants were placed in a 3-neck, round-bottom flask equipped with a reflux condenser, thermometer and mechanically driven stirrer. The mixture was then heated for a period of 5 hours at 119 C. The product, an amorphous, pale brown, insoluble material, was isolated from the solvent layer by decantation and then dissolved in acetone. By pouring this solution into methanol, filtering and drying the precipitate, there was obtained 84 grams of a pale brown, amorphous powder containing 4.8% sulfur. A saponification value of 519 indicated that the product contains 45.3% by weight maleic anhydride.

EXAMPLE IV Z-T-BUTYLTH'IOPHENE-IVIODIFfED STYRENE-MAL IG ANHYDRIDE -COPOLYMER Reaction mixture Maleic anhydride "grams" 49 Styrene do 52 Z-t-butyl thiophene cc 250 Benzoyl peroxide gram 1.0

These reactants were placed in a 3-neck, round-bottom flask equipped with a reflux condenser, thermometer and mechanically driven stirrer. The mixture was then heated for a period of 2 hours at C. The product, a brittle, insoluble material, was then isolated by filtration and dissolved in acetone. By pouring this solution into methanol, filtering and drying the precipitate, there was obtained 79.5 grams of a pale brown, amorphous powder containing 2.1% sulfur. A saponification value of 531 indicated that the product contains 46.5% by weight maleic anhydride.

EXAMPLE V 2,5-DI-T-BUTYL THIOPHENE-MODIFIED STYRENE- MALEic ANHYDRIDE COPOLYMER Reaction mixture Maleic anhydride grams 49 Styrene do 52 Benzoyl peroxide "gram" 1.0 2,5-di-t-butyl thiophene cc 250 These reactants were placed in a 3-neck, round-bottom flask equipped with a reflux condenser, thermometer and mechanically driven stirrer. The mixture was then heated to 80 C. and as the result of a violently exothermic reaction the temperature rose to C. The product, a brittle insoluble material, was then isolated by decantation and dissolved in acetone. By pouring this solution into methanol, filtering and drying the precipitate, there was obtained 82 grams of a pale brown, amorphous powder containing 1.66% sulfur. A saponification value of 495 indicated that the product contains 43.2% by weight of maleic anhydride.

the aid of the refluxing xylene solvent.

EXAMPLE v1 3-ME'IHYL THIOPHENE MoDIFIED STYRENE MALErc ANHYDRIDE 'OOIOLYMER (XYLENE SOLVENT AND A Mon. EQUIVALENT OF 3-METHYL THIOPHENE) Reaction mixture Maleio anhydride grams /2 mole) 49 Styrene do' 52 3-methyl thiophene do 49 Benzoyl peroxide gram 1.0 Xylene cc 600 The reactants were placed in a 3-neck, round-bottom flask equipped with a reflux condenser, thermometer and mechanically driven stirrer. The mixture was then heated to 125 C. and as a result of an exothermic reaction, the temperature rose to 140 C. After cooling to 115 C. the mixture was maintained at this temperature for one hour. The product, an almost white, xylene-insoluble, amorphous solid, was filtered from the reaction solvent by means of a Buchner funnel. Further purification was accomplished by dissolving the polymer in acetone (300 cc.) and pouring this solution into methanol (1500 cc.). The precipitated product, after separation and drying, was a white, amorphous powder weighing 79 grams and containing 0.79% sulfur.

EXAMPLE VII sTYItENE-MALEIG ANHYDRIDE C'OIOLYMER (XYLENE SOLVENT) Reaction mixture Maleic anhydride grams 49 Styrene do 52 Xylene cc 600 Benzoyl peroxide Igram 1.0

EXAMPLE VIII DI LOROLB ESTER or THE THIorHENE-B IoDmrED STYBENE-MAIEIG. ANHYDRIDE COPOLYMER. OF Ex- AMPLE I Reaction mixture Thiophene-modified styrene-maleic anhydride copolymer (Example I) -grams 15.0 Lorol-B do 40.0 Xylene cc 200 Sulfuric acid (98%) cc 0.3

The reaction mixture was placed in a one-liter, three-neck flask equipped with a thermometer, mechanical stirrer and condenser. Between the condenser and flask was placed a Dean and Stark moisture trap fitted with a stopcock for removing water and solvent when so desired. A short while after the mixture had been heated at the reflux temperature of 140-150 0., the suspended copolymer gradually reacted to form the half ester. The homogeneous solution thus obtained was then maintained at this temperature for about 3 hours, during which time the water of reaction slowly distilled over into the moisture trap, with The xylene was then permitted to distill off until the temperature of the reaction mixture had reached 160 C. After remaining for about 15 minutes at this temperature, the product was permitted to cool to room temperature. The viscous composition was then diluted with cc. of benzol and stirred with about 10 grams of sodium bicarbonate to neutralize the acidic catalyst. After filtration through Hi-Flo clay, the filtrate was topped to 300 C. at 5 mm. pressure to remove solvents and unreacted Lorol alcohol. The product, a light brown, tacky material, had a neutralization number of 6.0, indicating that essentially complete esterification of the copolymer had taken place. The sulfur content of the finished product was 0.82%.

The product of Example VIII was free of mineral oil in the finished form. Some of the products in the following examples were blended with mineral oil to the extent of 75%, to lower the viscosity of the additive and thus facilitate further blending operations. All concentrations of the various esters evaluated are, however, reported on the basis of mineral oil-free products.

EXAIVIPLE IX D1 LoBoL-B ESTER or THE 2-METHYL THIOPHENE- MoDIFIED STYRENE-MALEIo ANHYDRIDE GoPoLYMER 0F EXAMPLE II Reaction mixture 2-methyl thiophene-modified styrene-maleic anhydride copolymer (Example II) grams 15.0 Lorol-B do 37.5 Xylene cc 200 Sulfuric acid (98%) cc 0.3

The same general procedure was followed as outlined in Example VIII.

EXAMPLE X Dr LoRonB ESTER, or THE 3-METHYL THIOPHENE- MODIFIED STYRENE-HALEIO ANHYDRIDE COPOLYMER 0F EXAMPTE III 1 Reaction mixture 3-methy1 thiophene-modified styrene-maleic anhydride copolymer (Example III) grams 15.0

Lorol-B do 37.5 Xylene cc 200 Sulfuric acid (98%) cc 0.3

The same general procedure was followed as outlined in Example VIII.

EXAMPLE XI DI LonoL-B ESTER or THE 2-T-BUTYL THIOPHENE- MoDIFIED STYRDNE-MALEIC ANHYDBIDE COPOLYMER 0F EXAMPLE IV Reaction mixture Z-t-buty]. thiophene-modified styreneuna leic anhydride copolymer (Example IV) grams" 15.0 -Lorol-B do 37.5

Xylene cc 100 Sulfuric acid (98%) cc 0.3

The same general procedure was followed as outlined in Example VIII.

DI L BOL-B ESTER OF THE 2,5-DI-T-BUTYL TH1o PHENE-\IOI )IFIED STXRENE-MALEIC ANHYDRIDE Co- PoLYM F EXAMPLE V Reaction mixture 2,5-di-t-butyl thiophene-modified styrenemaleic anhydride copolymer (Example V) grams 15.0 "Lorol-B do 37.5 Xylene cc 100 Sulfuric acid (98%) cc 0.3

The same general procedure was followed as outlined in Example VIII.

EXAMPLE XIII DI LoRoL-B ESTER OF THE 3-METHYL THIOPHENE- MODIF ED STYRENE-MALEIo ANI-IYDRIDE COPOLYMER 0F EXAMPLE VI Reaction mixture E-methyl thiophene-modified styrene maleic anhydride copolymer (Example VI) grams 15.0 Lorol-B do 37.5 Xylene cc 200 Sulfuric acid (98%) cc 0.3

The same general procedure was followed as outlined in Example VIII.

EXAMPLE XIV DI LoRoL-B EsTER OF THE STYRENE-MALEIQ ANHY- DRIDE GoPoLYMER 0F EXAMPLE VII Reaction mixture The same general procedure was followed as outlined in Example VIII.

EXAMPLE XV-A DI-DECYL ESTER OF THE 3-METHY1L THIOPHENE-MQDI- FIED STYRENE-MALmo ANHYDRIDE GoPoLYMER OF EXAMPLE VI Reaction mixture 3-methy1 thiophene-modified styrene-maleic anhydride copolymer (Example VI) grams 15.0 l-decanol do 29.0 Xylene cc 200 Sulfuric acid (98%) cc 0.3

EXANLPLE XV-B DI-DODECYL ESTER OF THE 3-METHYLTHIoPHENE-Mon- IFIED STYRENE-MALEIO ANHYDRIDE COPQLYMER OF EXAMPLE VI Reaction mixture 3-methyl thiophene-modified styrene-maleic anhydride copolymer (Example VI) EXAMPLE xv-o DI-TETRADECYL EsTER OF THE 3-METHYL THIOPHENE- MODIFIED STYRENE-MALEIQ ANHYDRIDE COIOLYMER on EXAMPLE VI Reaction mixture 3-methyl thiophene-modified styrene-maleic anhydride copolymer (Example VI) grams 15.0

l-tetradecanol do 37.5

Xylene cc 200 Sulfuric acid (98%) cc 0.3

EXAMPLE XV-D DI-HEXADECYL ESTER OF THE g-METHYL 'lHIOPHENE- MODIFIED STYRENE-MALEIC ANHYDRI'DE CoPoLYMER OF EXAMPLE VI Reaction mixture 3-methyl thiophene-modified styrene-maleic anhydride copolymer (Example VI) grams 15.0 l-hexadecanol do 45.0 Xylene cc 200 Sulfuric acid (98%) cc 0.5

EXAMPLE XV-E DI-OGTADECYL EsTER on THE 3-METHYL TI-IIOPHENE- M'oDIFIED STYRENE-MALEIC ANHYDRIDE COPOLYMER OF EXAMPLE VI Reaction mixture 3-methy1 thiophene-modified styrene-ma- The same general procedure was followed for these products as outlined in Example VIII.

POUR POINT DEPRESSION AND V. I. IMPROVEMENT To demonstrate the effectiveness of the various products in reducing the pour point and increasing the viscosity index of lubricating oils, the results obtained in tests conducted on blends of the various products in various proportions in lubricating oils are presented in Tables I and II.

Two different base oils were used in these tests, oil A being a solvent-refined Mid-Continent, SAE 30 grade oil, having a kinematic viscosity at 210 F. of 11.96 and a 20 F. pour point, and oil B being an acid-refined, Mid-Continent stock with a kinematic viscosity at 100 F. of 30.49, a kinematic viscosity at 210 F. of 4.83 and a viscosity index of 80.1.

Table I shows the effect of varying the type of thiophene derivative utilized in modifying the styrene-maleic anhydride copolymer, while Table II shows the effect of varying the ester chain length of the 3-methyl-thiophene-modified copolymer. It will be observed from Table I that the best results were obtained with the copolymers modified with the branched-chain alkyl Table I in 011A ASTM PourPoint V. I. of 1% Blend in Oil B Ex. N0. Thiophene Compound Type Ester Kin. Vis. Kin. Vis.

Ex. No. Thiophenc Compound Type Ester 1% 54% W70 6% Vis. Vis.

Kin. Kin. L

XVA 3-1\I(ejthyl'lhi0phene. l-Decanol...

XVB l-Dodccanol. +20 XVC- ..do l-Tetradecanol. XVD. ...do l-Hexadecanol. XV-E... ..do l-Octadecanol.

CORROSION INHIBITION As mentioned hereinbefore, an added advantage of our new thiophenemodified products is their ability to prevent corrosion of metal surfaces. To demonstrate this ability several of the products were tested in the Socony-Vacuum bubble test. In this test a connecting rod bearing having a Cd-Ag alloy surface is carefully weighed and placed in a 200 x mm. test tube together with grams of the test oil. The test tube is placed in a constant temperature bath and air blown through the test oil at the rate of 2 liters per hour for the required time (22 hours) at a temperature of C. The test piece is then removed and weighed for loss in weight. The results are reported in mgms. of weight loss. The results obtained in several such tests, conducted on blends of the various products in a solvent refined oil having a kinematic viscosity of 8.2 at 210 F., are given in Table III. As can be observed from the data, the product of Example XIV, which was not modified with a thiophene compound, does not prevent bearing corrosion, whereas the thiophene-modified products provide substantial corrosion inhibition.

Although, as demonstrated herein, oils containing 1 5% of the products of the invention are markedly improved, significant improvement will be obtained by the use of as little as .01%. Furthermore, although amounts up to about 1% are generally sufficient, in certain applications as much as 10% of the additive compounds are used. Also, it is contemplated that the products of the invention be incorporated in greater concentration, i. e. above 10%, to provide concentrates of these materials in oil for marketing, such concentrated compositions affording a readily soluble form of the additive'materials for dilution with further quantities of oil prior to actual use.

The oils in which our new addition agents are incorporated, or the oil concentrates. may also contain other addition agents, designed to improve the character of the oil in other respects, such as extreme pressure quality, detergency, etc.

Although the principles of the invention have been illustrated herein by means of certain specific examples and tests, it is not intended that the scope of the invention be limited thereby, but

only as indicated in the appended claims.

Table III i ggl 'i ii l i u e est eating Product Concentration of Additive Product ample No. Blank 2% 1% m. we

VIII Di Lorol-B" Ester of the Thiophene 14 5 20 ModifiedStyrene-MaleicAnhydride Copolymer. X Di Lorol-B Ester of the 3-Methyl 0 l 20 Thiophene Modified Styrene-Maleic Anhydride Oopolymer. XI Di Lorol-B" Ester of the l-t-Butyl 4 6 24 Thiophene Modified Styrene-Maleic Anhydride Copolymer. XIV Di Lorol-B" Ester of the Styrene- 24 34 l8 Maleic Anhydride Copolymer.

We claim:

1. A mineral lubricating oil containing a minor amount, sufficient to improve the viscosity index of said oil, of a reaction product prepared -by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (1)) about 1 mol of styrene and (c) from about 1 to about 10 mols of a thiophene compound selected from the group consist: ing of thiophene and alkyl-substituted thiophenes, at a temperature of from about 75 C. to about 125 C., and (2) esterifying the product obtained in step 1 with a primary, normal, saturated alcohol having from about 10 to about 18 carbon atoms.

2. A mineral lubricating oil containing a minor amount, from about 0.01 per cent to about 10 per cent, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about 10 mols of a thiophene compound selected from the group consisting of thiophene and alkyl-substituted thiophenes, at a temperature of from about 75 C. to about 125 C., and (2) esterifying the product obtained in step 1 with a primary, normal, saturated alcohol having from about 10 to about 18 carbon atoms.

3. A mineral lubricating oil containing a minor amount, sufficient to depress the pour point of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from'about 1 to about 10 mols of a thiophene compound selected from the group consisting of thiophene and alkyl-substituted thiophenes, at a temperature of from about 7 C. to about 125 C., and (2) esterifying the product thus obtained with a primary, normal, saturated alcohol having from 14 to 16 carbon atoms.

4. A mineral lubricating oil containing a minor amount, sufiicient to depress the pour point of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about mols of a thiophene compound selected from the group consisting of thiophene and alkyl-substituted thiophenes, at a temperature of from about 75 C. to about 125 C., and (2) esterifying the product thus obtained with a mixture of primary, normal, saturated alcohols having an average of about 14 carbons per molecule.

5. A mineral lubricating oil containing a minor amount, sufiicient to improve the viscosity index of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about 10 mols of 2-tertiary-butyl thiophene and (2) esterifying the product obtained in step 1 with a primary, normal, saturated alcohol having from about 10 to about 18 carbon atoms.

6. A mineral lubricating oil containing a minor amount, sufiicient to improve the viscosity index of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and 12 (c) from about 1 to about 10 mols of 2-tertiarybutyl thiophene and (2) esterifying the product obtained in step 1 with a mixture of primary, normal, saturated alcohols having an average of about 14 carbon atoms per molecule.

7. A mineral lubricating oil containing a minor amount, suflicient to improve the viscosity index of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about 10 mols of 2-methyl thiophene and (2) esterifying the product obtained in step 1 with a primary, normal, saturated alcohol having from about 10 to about 18 carbon atoms.

8. A mineral lubricating oil containing a minor amount, suflicient to improve the viscosity index of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about 10 mols of 2-methyl thiophene and (2) esterifying the product obtained in step 1 with a mixture of primary, normal, saturated alcohols having an average of about 14 carbon atoms per molecule.

9. A mineral lubricating oil containing a minor amount, suincient to improve the viscosity index of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about 10 mols of thiophene and (2) esterifying the product obtained in step 1 with a mixture of primary, normal, saturated alcohols having an average of about 14 carbon atoms per molecule.

10. A mineral lubricating oil containing a minor amount, sufiicient to depress the pour point of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about 10 mols of 2,5-ditertiary-butyl thiophene and (2) esterifying the product obtained in step 1 with a mixture of primary, normal, saturated alcohols having an average of about 14 carbon atoms per molecule. I 11. A mineral lubricating oil containing a minor amount, suificient to depress the pour point of said oil, of a reaction product prepared by the steps of (1) reacting together (a) about 1 mol of maleic anhydride, (b) about 1 mol of styrene and (c) from about 1 to about 10 mols of 3-methyl thiophene and (2) esterifying the product obtained in step 1 with tetradecyl alcohol.

FERDINAND P. o'rTo. ORLAIND M. REIFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 2,496,669 Meadow Feb. 7, 1950 

1. A MINERAL LUBRICATING OIL COMTAINING A MINOR AMOUNT, SUFFICIENT TO IMPROVE THE VISCOSITY INDEX OF SAID OIL, OF A REACTION PRODUCT PREPARED BY THE STEPS OF (1) REACTING TOGETHER (A) ABOUT 1 MOL OF MALEIC ANHYDRIDE, (B) ABOUT 1 MOL OF STYRENE AND (C) FROM ABOUT 1 TO ABOUT 10 MOLS OF A THIOPHENE COMPOUND SELECTED FROM THE GROUP CONSISTING OF THIOPHENE AND ALKYL-SUBSTITUTED THIOPHENES, AT A TEMPERATURE OF FROM ABOUT 75* C. TO ABOUT 125* C., AND (2) ESTERIFYING THE PRODUCT OBTAINED IN STEP 1 WITH A PRIMARY, NORMAL, SATURATED ALCOHOL HAVING FROM ABOUT 10 TO ABOUT 18 CARBON ATOMS. 